Means for extending and retracting boom sections of a crane



Dec. 2, 1969 R. E. sTAuFFER MEANS FOR EXTENDING AND RETRACTING BOOMSECTIONS OF A CRANE 2 Sheets-Sheet l Filed Deo. 5, 1967 /N VEA/rol?ROBERT ESTAUFFER, BY m United States Patent O 3,481,489 MEANS FOREXTENDING AND RETRACTING BOOM SECTIONS F A CRANE Robert E. Staufer, 119Edgewood Drive, Galion, Ohio 44833 Filed Dec. S, 1967, Ser. No. 688,236Int. Cl. B66c 23/06; F02b 73/00 U.S. Cl. 212-55 3 Claims ABSTRACT 0F THEDISCLOSURE The instant invention relates to cranes that have a boom withseveral relatively extensible and retractable boom sections, and moreparticularly to an improved system for extending and retracting the boomsections relatively to each other.

Cranes find widespread applications for use in lifting and moving loadsof various types. The cranes customarily `include a boom which is usedto reach out to the load, and by which the load is picked up and movedto another location at which the load is set down. The crane boom isusually supported on a turntable base which permits movement of the boomto any position within the circle of operation of the crane. The boom ismounted on a pivot to permit the boom to be raised and lowered in orderto reach to various elevations. In addition to these movements the boomis formed with several boom sections that may be extended and retractedrelatively to each other in order to reach out in the radial directionto a particular location.

In one type of crane construction with a boom that has severalextensible and retractable boom sections, the boom sections aretelescoped within each other in -the retracted condition of the boom.Each successive boom section is of smaller lateral `dimension than thepreceding boom section, in order to permit the telescoping operation.When the several boom sections are fully extended, the boom has theconfiguration of a taperingcantilever beam, since the boom sections areof successively smaller lateral dimension.

In the tapering beam configuration of the extended boom the Weakest partof the boom is that part which is of smallest lateral dimension, and theboom is of greater strength in the successively larger sections. InA thecourse of operating the crane it is customary to extend and retract theseveral sections of the boom while there is a load supported on the endof the boom. The several boom sections must be of sufficient strength tosupport the load which is carried by the boom. In order to mosteffectively operate the boom in its extensive and retractive movements,the several boom sections are extended and retracted at proportionalrates of movement, which may Ebe equal, so that the tapering vbeamconfiguration of the boom is maintained in all steps of extension andretraction of the boom sections, in order to most effectively distributethe load on the boom.

It is an object of this invention to provide an improved system forextending and retracting the several boom sections of the boom in acrane.

It is another object of this invention to provide a crane 3,481,489Patented Dec. 2, 1969 ICC in which the several sections of the boom areextended and retracted relatively to each other at proportional rates ofmovement.

It is a further object of this invention to provide an improved crane inwhich the boom has several boom sections of successively smallerdimension, and in which the boom sections are extended and retracted atproportional rates of movement to maintain a tapering beam configurationof the boom in all positions of extension and retraction of the boomsections.

Still another object of this invention is to provide a crane in whichthe boom has several boom sections that are of successively smallerdimension to be telescopically received within each other, and the boomsections are extended and retracted relatively to each other at equalrates of movement, in order to maintain the tapering beam configurationof the boom.

Other objects of the invention will appear hereinafter, the novelfeaures and combinations being set forth in the appended claims.

Referring to the drawings:

FIG. 1 is a side elevational view of a crane boom constructed inaccordance with this invention;

FIG. 2 is a diagrammatic illustration of the hydraulic system forextending and retracting the boom sections; and

FIG. 3 is a sectional view of the flow divider valve.

Referring to FIG. l, there is illustrated alcrane boom 10 which issupported on a base 11, which may be the frame or chassis of a truck bywhich the crane is moved to different work locations. There is aturntable 12 on the supporting base 11, zby which the crane boom 10 maybe swung to any position in the circle of operation of the crane boom10. A pedestal 13 stands on the turntable 12,

and extends upwardly and rearwardly to support a lateral pivot pin 14,on which the boom 10 is mounted. A lift cylinder 15 is placed in thepedestal 13. The base end of the cylinder 15 is connected to theturntable 12 by a pivot pin 16, and the piston rod end of the cylinder15 is connected to the boom 10 by a pivot pin 17. The boom 10 is swungupwardly on the pivot pin 14 to an elevated position lby extension ofthe cylinder 15, in order to reach to different elevations. The boom 10is lowered by contraction of the cylinder 15.

The boom 10 extends forwardly from the pedestal 13 as a cantilever beam,and is counterbalanced by a counterweight 18 rearwardly of the pivot 14.The counterweight 18 Vis secured to a rearward extension 19 of the firstor lower boom section 20. A winch 21 is placed at the rear end of theboom 10, partially within the counterweight 18, and is also secured tothe rearward extension 19. A winch line 22 extends from the winch 21over the top of the boom 10 to the head `block 23 at the forward end ofthe boom 10. The line 22 is reeved around the sheaves 24, 25 in the headIblock 23, and around the sheave 26 in the hook block 27. The winch line22 may be taken up and let out from the winch 21 by operation of thelatter, which respectively raises or lowers the head block 27 to raiseor lower the load which is secured or held on the hook 28.

The first boom section 20 is formed with a hollow walled construction toreceive a second or upper boom section 30, which is telescoped into thefirst boom section 20 and may be extended and retracted relatively tothe latter. The second boom section 30' is also formed with a hollowwalled construction to telescopically receive the third boom section 31,which may be extended and retracted relatively to the second boomsection 30. The head block 23 is secured to the outer end of the thirdboom section 31.

There is a first hydraulic cylinder 32 which is disposed at the bottomof the first boom -section 20 and extends longitudinally along the firstboom section 20. The cylinder 32 is secured to the first boom section 20at approximately mid-length of the cylinder 32 by a plurality ofyieldable mounting, elements 33, which permit the cylinder 32 to yieldin response to the bending of the boom under load. The piston rod end ofcylinder 32 is connected to the second boom section 30 by a pin 34 and adepending foot 35, of which the latter is secured to the second boomsection 30. The hydraulic cylinder 32 includes the usual piston andpiston rod which are linearly movable, and upon extension of the pistonrod the second boom section 30 is extended relatively to the boomsection and retraction of the piston rod retracts the second boomsection to its telescoped disposition within the first boom section 20.

There is a second hydraulic cylinder 38 which is disposed within thesecond and third boom sections 30, 31. When the second boom section 30is moved relatively to the first boom section 20, the third boom section31 moves with the second boom section 30, and the second cylinder 38also moves, since is connected to the second and third boom sections 30,31.

The cylinder or base end of the second hydraulic cylinder 38 isconnected to the second boom section 30 by an upright pin 39. The pistonrod end of the second hydraulic cylinder 38 is connected to the thirdboom section 31 by a pin 40 in an upright leg 41 that is secured to thesecond boom section 30 is retracted, the coil spring 45 38 includes theusual piston and piston rod, which are linearly movable. By extensionand retraction of the piston rod of the second cylinder 38, the thirdboom section 31 is extended and retracted relatively to the second boomsection 30.

Each of the hydraulic cylinders 32, 38 is double acting, and therefore,is power operated on the extension stroke and on the retraction strokethereof. Hydraulic operating fluid under pressure is supplied to thefirst and second cylinders 32, 38 at the base ends thereof for extendingthe boom sections 30, 31, or alternatively, hydraulic fluid underpressure is supplied to the piston rod ends of the cylinders 32, 38 inorder to retract the boom sections 30, 31.

There are the usual hydraulic hoses connected to the cylinders 32, 38,but these are not illustrated in FIG. 1 in the interests of maintainingclarity of the drawing. The cylinder 32 is supported on the first boomsection 20 and does not travel. However, the second hydraulic cylinder38 travels with the second and third boom sections 30, 31. Therefore,the hydraulic hoses for the second hydraulic cylinder 38 are led arounda movable sheave 42 to a fixed sheave 43, and then into the second boomsection 30, to be connected to the second cylinder 38. The movablesheave 42 may travel along a rail 44 that extends longitudinally alongthe rst boom section 20. A long coil spring 45 urges the movable sheave42 to its forwardmost position, as illustrated in FIG. 1. When thesecond boom section 30 is extended relatively to the first boom section20, the hydraulic hoses are drawn around the fixed sheave 43, pullingthe movable sheave 42 rearwardly against the force of the coil spring45. When the second boom section 30 is retracted, the coil spring 45pulls the movable sheave 42 forwardly along the rail 44, thereby pullingthe hydraulic hoses out of the boom over the fixed sheave 43.

There is a guard 46 for the first hydraulic cylinder 32. Such guard 46extends along the underside of the cylinder 32, and there is a movableguard section 47 that moves outwardly with the second boom section 30when the latter is extended, to guard the piston rod of the cylinder 32.

Referring to FIG. 2, there is illustrated therein the hydraulicoperating system for the first and second hydraulic cylinders 32, 38, bywhich the several boom sections are extended. The hydraulic fluid issupplied under pressure by a pump 50 to a manual valve 51, which in itscentered position directs the liuid to the tank 52. The valve 51 may beoperated in one direction to direct the hydraulic operating fluid to theline 53, and the return hydraulic fluid from line 54 is directed throughthe valve 51 to the tank 52. The valve 51 may be operated in theopposite direction to direct the hydraulic operating fiuid from the pump50 to the line 54, and the line 53 then is the return line, and thereturn hydraulic operating fluid is then directed by the valve 51 to thetank 52. The valve 51 has return springs for the Valve spool to returnthe latter to its centered position in either direction of operation ofthe spool.

The line 53 is connected toa pressure compensated flow divider valve 55,which has the function of proportionally dividing the supply flow ofhydraulic operating fluid from the line 53 into two supply fiows ofoperating fluid in lines 56, 57. When the line 53 functions as a returnline for the hydraulic fluid, the flow divider valve 55 functions toproportionally combine the return flow of hydraulic fiuid from the lines56, 57 to the return line 53.

The line 53 functions as la supply line for hydraulic fluid when thesecond and third boom sections 30, 31 are extended by extension of thesecond and third cylinders 32, 38, respectively. The supply flow ofhydraulic fiuid is through the line 56, the check valve 58 and line 59,the latter being connected to the base or cylinder end of the firstcylinder 32. The operating fluid from the line 59 extends the piston andpiston rod of the cylinder 32. The return hydraulic fiuid from thepiston rod end of the cylinder 32 flows through the return line 60, theline 54 and the valve 51 to the tank 52.

The line 57 from the ow divider valve 55 is also a supply line forhydraulic operating liuid under pressure, and such hydraulic fiuid flowsthrough the line 57, the check valve `61 and the line 62 to the base orcylinder end of the second cylinder 38 to extend the piston and pistonrod thereof. The return flow of hydraulic fiuid is from the piston rodend of the cylinder 38 through the line 63, the line 54 and the valve 51to the tank 52.

When the second and third boom sections 30, 31 have been extended to thedesired point of extension by operation of the first and secondcylinders 32, 38, as described above, the valve 51 is returned to itscentered or neutral position. The check valves 58, 61 block the returnflow of hydraulic fluid from the base or cylinder ends of the cylinders32, 38, respectively, which holds the latter in their selected extendedpositions.

The line 54 functions as the supply line for the hydraulic operatingfluid under pressure when the second and third boom sections 30, 31 areretracted. The hydraulic operating fluid iiows through the line 54 andthe line 60 to the piston rod end of the first cylinder 32 to retractits piston rod. The supply hydraulic liuid from the line 60 also flowsinto the pilot line 64 which opens the pilot operated relief valve 65for return iiow of hydraulic iiuid from the base or cylinder end of thefirst cylinder 32 through the line 59, the relief valve 65 and the line56 to the flow divider valve 55.

The supply hydraulic fluid for the second cylinder 38 flows through theline 54 and the line 63 to the piston rod end of the second cylinder 38to retract its piston rod. The supply hydraulic iiuid also flows to thepilot line 66 to open the pilot operated relief valve 67 for return flowof hydraulic uid from the base end of the second hydraulic cylinder 38through the line 62, the relief valve 67 and the line 57 to the owdivider Valve 55.

The return flows of hydraulic fiuid from the lines 56, 57 are combinedat proportional rates of flow by the iiow divider valve 55 into the line53 leading to the control valve 51 and then to the tank 52. The flowdivider valve 55 combines the return flows of hydraulic uid from thelines 56, 57 to the line 53 at the same proportional rates of liow asthe divided rates of flow of the supply hydraulic fluid.

The flow divider valve 55 divides the supply flow of hydraulic fluid soas to provide two predetermined proportional rates of flow of fluid tothe first and second hydraulic cylinders 32, 38. The rates of extensionof the first and second hydraulic cylinders 32, 38 is then commensuratewith the predetermined proportionally divided flow rates of hydraulicfluid as supplied through the flow divider valve 55. In this manner, thesecond and third boom extensions 30, 31 are extended at the same time atproportional rates so that the tapering beam configuration of the -boomis maintained in all positions of extension of the crane boom 10. Theflow divider valve 55 functions in the same manner to combine the returnflows of hydraulic fluid from the first and second cylinders 32, 38. Thereturn flows of hydraulic fluid are combined at the predeterminedproportional rates of flow, and accordingly, the second and third boomextensions 30, 31 are retracted at rates that are commensurate with saidpredetermined proportional rates of flows of the return hydraulic fluidfrom the respective cylinders 32, 38.

The hydraulic circuit includes a relief valve 68 which is connectedacross the flow divider valve 55 from the line 56 to the line 57. If thefirst cylinder 32 should complete its stroke and bottom out before thesecond cylinder 38 completes its stroke, then the flow in line 56 isblocked. The increased pressure of the fluid in line 56 is operative toopen the relief valve 68 to permit the flow of hydraulic fluid to theline 57, with the effect that the second cylinder 38 receives the totalsupply of fluid to complete its stroke.

There is a second relief valve 69 which is connected from the line 57 tothe line 56. If the second cylinder 38 should complete its stroke andbottom out before the first cylinder 32 completes its stroke, then thesecond relief valve 69 opens in response to the increased pressure ofthe fluid to permit flow of hydraulic fluid to the line 56, so that thefirst cylinder 32 then receives the total supply of uid to complete itsstroke.

The flow divider valve S5 is illustrated in FIG. 3. There is a valvebody 71 with a valve port 72, a first cylinder port 73, and a secondcylinder port 74. The line 53 connects to the valve or inlet port 72,the line 56 connects to the cylinder or outlet port 73, and the line 57connects to the cylinder or outlet port 74, as represented in FIG. 3.

At the one side of the flow divider valve 55 there is a first sleeve 75which is retained in the valve body by a threaded end cap 76. A firstspool 77 is slidably received in the first sleeve 75, with a coil spring78 disposed between the end cap 76 and the spool 77 to urge the latterto the right, as viewed in FIG. 3. The spool 77 has several orifices 79which communicate with the valve port 72. The spool 77 has several moreorifices 80 which are downstream of the orifices 79. The sleeve 75 hasseveral orifices 81, which are disposed adjacent to and in communicationwith the orifices 80. The flow of hydraulic fluid is from the valve port72, through the orifices 79, through the orifices 80, and then throughthe orifices 81 to the cylinder port 73.

The other side of the flow divider valve 55 is identical to the leftside thereof, which has been described above. There is a second sleeve85 which is received in the valve body 71 and secured therein by athreaded end cap 86. A second spool 87 is slidably received in thesleeve 85, and there is a coil spring 88 that is disposed between thesecond spool 87 and the threaded end cap 86 to urge the second spool 87to the left, as viewed in FIG. 3. The spool 87 has several orifices 89which communicate with the valve port 72. The second spool 87 hasseveral more orifices 90 which are downstream from the orifices 89. Thesleeve 85 has several orifices 91 which are adjacent to the orifices 90and in communication therewith. The flow of hydraulic fluid is from thevalve port 72 through the orifices 89, through the orifices 90, andthrough the orifices 91, to the cylinder port 74.

The first spool 77 has a claw 92 which extends towards the center of thevalve 55. The second spool 87 has a similar claw 93, which also extendstowards the center of the valve 55. The claws 92, 93 are engaged tomechanically link the first and second spools 77, 87. A coil spring 94surrounds the claws 92, 93 and acts against the first and second spools77, 87 in opposite directions.

In the flow divider valve 55 as illustrated in FIG. 3, the hydraulicfluid is proportionally divided into equal rates of flow of the supplyhydraulic operating fluid, or is proportionally combined at equal ratesof ow to maintain the return flows of hydraulic fluid at equal rates. Ifthe flow should tend to increase to the cylinder port 73, then there isa flow induced pressure drop across the first spool 77, which causes thespool 77 to shift its position to the left, as viewed in FIG. 3. Suchmovement of the first spool 77 produces a restriction of the flowpassage through the orifices 8.0, 81 until the proportionally dividedflows of hydraulic fluid are returned to equal rates of flow. The samemode of operation occurs with respect to the flow of hydraulic fluidthrough the second valve spool 87. The flow divider valve 55 acts insimilar manner with respect to the return flows of hydraulic fluid toproportionally combine such return flows of hydraulic fluid at equalrates of flow.

In the embodiment of the invention which is described herein, the secondand third `boom sections 30, 31 are extended and retracted at the sametime, and at the same rates of movement, so as to maintain the taperingbeam configuration of the iboom 10 in all positions of extension andretraction. In any construction in which the extensible and retractableboom sections are of different lengths, `such boom sections could beextended and retracted at the same time, and at different rates ofmovement that are proportional to the respective lengths of the boomsections, thus to maintain the tapering beam configuration of the boomin all positions of extension and retraction.

Obviously those skilled in the art may make various changes in thedetails and arrangement of parts without departing from the spirit andscope of the invention, and applicant therefore wishes not to berestricted to the precise construction herein disclosed.

Having thus described and shown an embodiment of the invention, what itis desired to secure by Letters Patent of the United States is:

1. An extensible and retractable lboom construction comprising, a firstboom section, a second boom section, a third boom section, power meansto extend and to retract said boom sections relatively to each other inwhich said second boom section forms an extension of said first boomsection and said third boom section forms an extension of said secondboom section, said power means including a first fluid operated actuatorand a second fluid operated actuator, means to connect said first fluidoperated actuator to said first boom section and to said second boomsection, means to connect said second fluid operated actuator to saidsecond boom section and to said third boom section, means to supplyoperating fluid for said power means to extend and to retract said boomsections relatively to each other, flow divider means for said operatingfluid to divide the operating fluid into predetermined proportionalrates of flow to said first fluid operated actuator and to said secondfluid operated actuator, respectively, in order to extend said second:boom section relatively to said first boom section and to extend saidthird boom section relatively to said second boom section at rates ofmovement that are commensurate with said predetermined proportonallydivided flow rates of fluid to said first and second actuators,respectively, a first pressure responsive relief valve connected in onedirection across said fiow divider means from said first fluid operatedactuator to said second fluid operated actuator to supply the combinedoperating fluid to the second fluid operated actuator when the operationof the first fluid operated actuator is restrained, and a secondpressure responsive relief valve connected in the opposite directionacross said flow divider means from said second fluid operated actuatorto said first fluid operated actuator to supply the combined operatingfluid to the first fiuid operated actuator When the operation of thesecond fluid operated actuator is restrained.

2. An extensible and retractable boom construction as recited in claim 1in which said flow divider means cornprises an inlet port for actuatingfluid, a first outlet port for actuating uid to said first fluidoperated actuator, a second outlet port for actuating fluid to saidsecond fluid operated actuator, a first flow restricting passage fromsaid inlet to said first outlet and a second ow restricting passage fromsaid inlet to said second outlet to proportionally divide the flow ofactuating fluid from said inlet port to said first outlet port and tosaid second outlet port, respectively, said first pressure responsiverelief valve being connected to said first outlet port of said flowdivider means, and said second pressure responsive relief valve beingconnected to said second outlet port of said flow divider means.

3. An extensible and retractable boom construction as recited in claim 1in which said flow divider means comprises an inlet port for actuatingiiuid, a first outlet port for actuating fluid to said first fiuidoperated actuator, a second outlet port for actuating fluid to saidsecond fluid operated actuator, a first flow restricting passage fromsaid inlet to said first outlet and a second ow restricting passage fromsaid inlet to said second outlet to proportionally divide the fioW ofactuating fluid from said inlet port to said first outlet port and tosaid second outlet port, respectively, said first pressure responsiverelief valve being connected to said first outlet port and to saidsecond outlet port of said flow divider means in one direction from thefirst outlet port to the second outlet port, and said second pressureresponsive relief valve being connected to said second outlet port andto said first outlet port of said ow divider means in the oppositedirection from the second outlet port to the first outlet port.

References Cited UNITED STATES PATENTS 2,643,664 6/1953 Willett 60972,882,688 4/1959 Billen 91-412 3,300,060 l/1967 Lado 212- 3,315,8214/1967 Grove 212-55 3,344,940 10/ 1967 Burgess 60--97 HARVEY C. HORNSBY,Primary Examiner U.S. Cl. X.R. -97; 91-412

